什么是丢包，为什么会丢包
PING 74.221.222.223 (74.221.222.223) 56(84) bytes of data.
64 bytes from 74.221.222.223: icmp_seq=1 ttl=51 time=234 ms
64 bytes from 74.221.222.223: icmp_seq=2 ttl=51 time=347 ms
64 bytes from 74.221.222.223: icmp_seq=3 ttl=51 time=250 ms
64 bytes from 74.221.222.223: icmp_seq=4 ttl=51 time=380 ms
64 bytes from 74.221.222.223: icmp_seq=5 ttl=51 time=287 ms
64 bytes from 74.221.222.223: icmp_seq=6 ttl=51 time=224 ms
64 bytes from 74.221.222.223: icmp_seq=7 ttl=51 time=473 ms
64 bytes from 74.221.222.223: icmp_seq=8 ttl=51 time=380 ms
64 bytes from 74.221.222.223: icmp_seq=9 ttl=51 time=287 ms
64 bytes from 74.221.222.223: icmp_seq=10 ttl=51 time=225 ms
64 bytes from 74.221.222.223: icmp_seq=11 ttl=51 time=329 ms
64 bytes from 74.221.222.223: icmp_seq=12 ttl=51 time=248 ms
64 bytes from 74.221.222.223: icmp_seq=13 ttl=51 time=246 ms
64 bytes from 74.221.222.223: icmp_seq=14 ttl=51 time=365 ms
64 bytes from 74.221.222.223: icmp_seq=15 ttl=51 time=260 ms
64 bytes from 74.221.222.223: icmp_seq=16 ttl=51 time=387 ms
64 bytes from 74.221.222.223: icmp_seq=17 ttl=51 time=298 ms
64 bytes from 74.221.222.223: icmp_seq=18 ttl=51 time=209 ms
64 bytes from 74.221.222.223: icmp_seq=19 ttl=51 time=234 ms
^C
--- 74.221.222.223 ping statistics ---
19 packets transmitted, 19 received, 0% packet loss, time 18019ms
rtt min/avg/max/mdev = 209.395/298.454/473.422/71.104 ms